Menu
Is there a way to 'mov'e a specific immediate byte-size number into a direct memory location? I.e.
MOV 10h,ffffh
to write the value 16 into the memory address 65535? If so, which opcode is that, orwould I have to store a memory address into a register first?
336
The x86 opcode bytes are 8-bit equivalents of iii field that we discussed in simplified encoding. This provides for up to 512 different instruction classes, although the x86 does not yet use them all.
x86 opcodes are 1 byte for most common instructions, especially instructions which have existed since 8086. Instructions added later (e.g. like bsf and movsx in 386) often use 2-byte opcodes with a 0f escape byte.
The mov instruction copies the data item referred to by its first operand (i.e. register contents, memory contents, or a constant value) into the location referred to by its second operand (i.e. a register or memory).
The x86 instruction set refers to the set of instructions that x86-compatible microprocessors support. The instructions are usually part of an executable program, often stored as a computer file and executed on the processor.
Yes. The opcode is C6. You should download a copy of the Intel ISA documents, which are freely available.
To your follow-up question: the full encoding of your example is:
c6 04 25 ff ff 00 00 10
opcode modr/m sib address immediate
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
